This was the second dedicated launch of the 3MV series (not including two “Object-Probes”). Like its predecessor (see Kosmos 27), it was also designed for atmospheric entry and then impact on Venus.

Although the probe was successfully sent towards Venus, ground controllers faced a series of major malfunctions in the spacecraft during its coast to the planet. These malfunctions included depressurization of the main spacecraft bus when the glass cover of a Sun-star attitude control sensor cracked.

Additionally, the internal radio transmitters of the spacecraft were automatically switched on at precisely the wrong time, i.e., during depressurization, when the gas discharge created high-voltage currents that shorted out the communications system. As a result, communications had to be conducted through transmitters on the 639-pound (290-kilogram) pressurized descent module.

Last contact was on May 25, 1964, by which time, controllers managed to conduct two major course corrections (at 348,000 miles and 8 to 8.7 million miles or 560,000 and 13 to 14 million kilometers from Earth respectively), the first time such actions had been performed on a Soviet interplanetary spacecraft. The second correction, however, imparted 66 feet per second (20 meters per second) less velocity than required, ensuring that the vehicle would not intersect with Venus. The inert spacecraft eventually flew by Venus on July 19, 1964 at a range of 68,351 miles (110,000 kilometers).

The Soviets named the vehicle Zond, the Russian word for probe, even though it was not one of the “Object-Probe” test-bed spacecraft. This was done to disguise the fact that it was a failed Venus mission. If it had actually succeeded in its Venus mission, it probably would have been named Venera 2. (Undoubtedly this has confused historians since this was not an “Object-Probe” mission). The Soviets later published some data on cosmic ray flux measured by Zond 1.


Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.

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